3. In a large bowl, combine the flour, oats, sugar, cinnamon, and salt. Use an electric mixer on low speed to mix, about 5 seconds. With the mixer on low add 1 cup of the butter one piece at a time and then the vanilla. Continue mixing on low until the mixture resembles damp sand, about 2 minutes.

4. Pour about two-thirds of the mixture evenly into the prepared pan and firmlypress it into a compact, even layer. Bake until golden around the edges, about 20minutes. While the crust bakes, add the remaining 2 Tbsp. butter and the brownsugar to the remaining oats mixture. Mix on low until damp clumps form, about 1 to 2 minutes; set aside.

5. Once raisins have softened, drain the orange juice into a medium saucepan andset raisins aside. Whisk in the cornstarch, sugar, and salt until smooth. Set the pan over medium heat and cook, whisking constantly until thickened, about 3 to 4minutes. Mix in the raisins and lemon juice, and remove from heat.

6. When crust is ready, pour the raisin filling onto the hot crust and spread it evenly over the surface. Sprinkle reserved topping mixture evenly over the filling, forming it into rough pea-sized clumps. Return pan to the oven and bake until topping is a deep golden brown, about 30 minutes. Cool pan on a wire rack to room temperature, about 2 hours. When cool, run a sharp knife aroundthe outer edges of the pan, then cut into 24 squares and serve. Store leftover bars in an airtight container up to 4 days, or freeze.